Diagnostic Instructions
Circuit/System Description
The vehicle communication interface module (VCIM) provides the cellular microphone with a supplied voltage on the cellular microphone signal circuit. When the microphone is in use, voice data from the user is sent back to the VCIM on the signal
circuit. The VCIM provides a ground for the microphone via the low reference circuit.
Reference Information
Schematic Reference
OnStar Schematics
Connector End View Reference
Cellular Communication Connector End Views
Description and Operation
OnStar Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the cellular microphone.
- Test for less than 10 Ω between the microphone low reference circuit and ground.
⇒ | If greater than the specified range, test the circuit for an open/high resistance. |
- Ignition ON, test for 9.5-10.5 V between the microphone signal circuit and ground.
⇒ | If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the VCIM. |
⇒ | If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the VCIM. |
- If all circuits test normal, replace the cellular microphone.
Repair Instructions